Web tension control means



Nov. 8, 1966 H. HASKIN, JR

WEB TENSION CONTROL MEANS Filed Jan. 27, 1965 INVENTOR LAWRENCE H. HASKIN,JR.

m E N R O n A United States Patent 3,283,982 WEB TENSION CONTROL MEANS Lawrence H. Haskin, 31:, Richmond, Va, assignor to The Inta-Roto Machine Company, Inc, Richmond, Va., a corporation of Virginia Filed Jan. 27, 1965, Ser. No. 428,504 9 Claims. (Cl. 226195) This invention relates generally to web tensioning apparatus, and more particularly to such apparatus adapted for maintaining substantially uniform web tension.

Dancer or shock rolls are used in web handling machinery to maintain generally uniform web tension. These rolls are movably mounted and spring biased in opposition to web pull so as to take up slack in the web or accommodate above average pull. The web tension is employed to actuate various control mechanism, and the prior dancer rolls fail to maintain sufiicient uniformity because of the slackening or increased tension of the spring resistance. Because of variation in the web tension, the control mechanism may unnecessarily be actuated or the tension may become so great that it causes the web to break.

Having in mind the defects of the prior art structures, it is the principal object of the present invention to provide web tensioning apparatus capable of maintaining substantially uniform web tension regardless of variation in web pull.

Another object of the invention is to provide web tensioning apparatus adapted to eliminate the burden on the web of actuating control mechanism regardless of variation in web pull.

Still another object of the invention is to provide web tensioning apparatus adapted to reduce the effectiveness of the mass of the dancer roll and its associated support upon the web.

A further object of the invention is to provide web tensioning apparatus adapted to maintain equilibrium between the dancer roll and the web.

A still further object of the invention is to provide web tensioning apparatus having simplicity of design, economy of construction and efficiency in operation.

Briefly, in accordance with the present invention, the dancer roll is journaled on a movable support and biased by spring means against the pull of the web in the usual manner. The movable support and spring means are, in turn, carried by a movable mount which also carries a valve having a spring biased operating plunger engaging the movable support. The valve controls a fluid operated jack or servomotor which is connected to the movable mount for moving the latter to counteract movement of the dancer roll support and maintain equilibrium.

The novel features that are considered characteristic of the invention are set forth with particularly in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawing, wherein like reference characters indicate like parts throughout the several figures and in which:

FIG. 1 is a side elevational view of one embodiment of the invention;

FIG. 2 is a sectional view taken along line 22 of FIG. 1;

FIG. 3 is an enlarged detailed sectional view of the servovalve control means of FIG. 1, and

FIG. 4 is a side elevational view of another embodiment of the invention.

Referring now more particularly to the drawings, specifically to FIG. 1, the web tensioning apparatus includes the usual dancer or shock roll journaled between a pair of support arm means 12 which are pivotally supported Patented Nov. 8, 1966 ice on mounting means 14. Spring means 16 between the arm means 12 and mounting means 14 bias the arm means to swing the roll 10 against the pull of a web W that is trained around the roll. The web may be of paper, cloth, synthetic plastic, metal foil or the like, and the spring urged roll maintains the tension of the web more or less uniform, but is subject to considerable variation depending upon the tension of the spring means 16 and the effect of the mass of the dancer roll 10 and the arm means 12 on the web.

When the dancer 10 and arm means 12 are in the position illustrated in FIG. 1, the web W has a given initial tension as the spring means 16- bias the arm means and dancer to an equilibrium position in which the web ten sion and spring biasing forces are counterbalanced. In accordance with the present invention, this condition is substantially maintained by movably mounting the mount ing means 14 on horizontally disposed bedrail means 18, and moving said mounting means according to variations in angulation of said arm means 12.

As better shown in FIG. 2, the bedrail means 18 consists of a pair of parallel, spaced left and right rails 18a and 18b upon which are slidably mounted the left and right mounts 14a and 14b of the mounting means 14, respectively. The pivot arm means 12 includes left and right pivot arms 12a and 12b, the lower ends of which are pivotally carried by mounts 14a. and 14b, respectively. The spring mean-s 16 consists of a pair of springs 16a and 16b connected between the pivot arms 12a: and 12b and mounts 14a and 14b, respectively. Stop means 20, including left and right-hand stops 20a and 20/5 on the mounts 14a and 14b, limit the extent of counterclockwise pivotal movement of the arms as viewed in FIG. 1.

In accordance with the present invention, servovalve means 22 are provided for sensing displacement of dancer roll 10 by sen-sing displacement of the pivot arm means 12 from the initial equilibrium position relative to mounting means 14. The servovalve means 22 control the operation of servomotor means 24 to effect displacement of the mounting means 14 relative to the bedrail means 18 in a direction effecting return of the dancer roll 10 to the initial equilibrium position relative to the mounting means 14.

The servovalve means 22 includes left and right-hand servovalves 22a and 22]) mounted on the left and righthand mounts 14a and 14b adjacent pivot arms 12a and 12b, respectively. The servomotor means 24 includes left and right-hand servomotors whose piston rods are connected with the left and right mounts 14a and 14b and operated by the servovalves 22a and 2217, respectively. The servovalve means 22 have operating plungers 26 which engage laterally extending brackets 28 on the arm means 12 and are actuated in accordance with any swinging movement of the arms. By sensing each of the arms and adjusting each of the mounts independently, the arms are maintained parallel and axial deviation of the roll 10 is precluded.

Only one of the servomotors 24 is shown in FIG. 1, but they are identical in structure and operation, and each includes a cylinder 30 that is pivotally anchored at one end to a fixed standard 32 and aligned alongside the adjacent bedrail. Slidably mounted in the cylinder 30 is a piston 34 having a piston rod 36 that extends through the free end of the cylinder 30 and is connected at its free end with the respective mount 14a or 14b. The cylinder 30 has two openings 38 and 40 respectively adjacent the ends thereof for the admission and release of pressure fluid for moving the piston 34.

Referring to FIG 3, each of the servovalves 22 includes a valve body 42 secured to the respective mount and containing a chamber 44 that slidably receives a plunger valve 46. The plunger valve contains an annular groove 48 that defines spaced lands 50 and 52. The plunger 26 extends from one end of the plunger valve 46 and through the adjacent end of the valve body 42 for engagement with the respective arm bracket 28. The plunger 26 has a collar 54, and a coil spring 56 surrounds the plunger between the collar 54 and the body 42 and biases the plunger into engagement with the bracket 28, or to the left as shown in FIG. 3.

The valve body 42 has an inlet orifice 58 opening into chamber 44 and connected by a conduit 60 with a source of pressure fluid P. The valve body 42 also has a pair of outlet orifices 62 and 64 connected by conduits 66 and 68 with the openings 38 and 40, respectively, in the respective servomotor cylinder 30. At its ends, the servovalve body 42 contains vent passages 70 and 72, respectively. In the illustrated embodiment, the fluid of the pressure system comprises compressed air, and consequently the ends of servovalve chamber 44 are vented to atmosphere. It is apparent, however, that in a liquid pressure fluid system, vents 70 and 72 would be connected with a sump.

When the dancer roll 10 is in the equilibrium position shown in FIG. 1, the valve plunger 46 is in the illustrated FIG. 3 position, wherein lands 50 and 52 close outlet orifices 62 and 64 to isolate the servomotor chamber from the pressure fluid supply orifice 58. When the dancer roll 10 is in the equilibrium position, the web W is under the desired or initial tension but upon a variation in web tension, the roll will be caused to swing one way or the other out of equilibrium position. If web tension is increased, it will pull the roll 10 against the spring means 16, to the right in FIG. 1, and if web tension is decreased, the spring means 16 will pull the roll against the Web W, to the left in FIG. 1. Any such deviation of the roll 10 will actuate the servovalve means 22 and servomotor means 24 to correct the situation and reestablish equilibrium.

Assume now that owing to an increase in web tension, doncer roll 10 is displaced to the right in FIG. 1 and swings arm means 12 in the clockwise direction. The servovalve means 22 effects shifting of the mounting means 14 to the right to reduce Web tension to the desired predetermined value. More particularly, clockwies movement of the arm means 12 causes the plungers 26 of the servovalve means 22 to be shifted to the right, FIG. 3, against the force of springs 56 and thereby shift the plunger valve 46 to the right within the valve chamber 44 so that the lands t and 52 uncover the orifices 62 and 64, respectively.

Upon shifting of the plunger valve 46 to the right, the right end of the servomotor cylinder 39 is vented to atmosphere via opening 38, conduit 66, valve orifice 62, valve chamber 44 and vent passage 70; and the left end of the servomotor cylinder 30 is pressurized by pressure fluid supplied from source P via conduit 60, valve orifice 58, valve groove 48, orifice 64, conduit 68 and opening 40. Consequently, piston 34, rod 36 and the associated mount 14 are shifted slightly to the right to decrease web tension, whereupon the spring means 16 pivot the arm means 12 in the counterclockwise direction, and valve plungers 26 are shifted to the left by the springs 56, so that the plunger valves 46 are shifted to the left.

When the plungers 26 are returned to their FIG. 3 positions, orifices 62 and 64 are closed by lands 50 and 52, respectively, so that the servomotor is isolated from the pressure source P and from atmosphere. The dancer roll and the arm means 12 have been returned to the equilibrium position relative to the mounting means14, whereupon the web tension is again balanced by the tension of spring means 16 because the movement to the right of the mounting means 14 causes the web tension to be returned to the desired value.

Assuming now that the web tension is reduced from the desired value, the dancer roll 10 and arm means 12 are displaced to the left by the spring means 16 in the counterclockwise direction relative to the mounting means 14. Consequently, the valve plungers 26 are shifted to the left by springs 56, whereupon the opposite ends of the servomotor means 24 are pressurized and vented, re-

spectively. Consequently, the mounting means 14 is shifted to the left to increase web tension which, acting on dancer roll 10, causes arm means 12 to be pivoted in the clockwise direction against the force of the spring means 16. When the roll 10 and arm means 12 reach the equilibrium position relative to the mounting means 14, in which tension of the spring means 16 balances web tension and the web tension is increased to its initial value, the plungers 26 are shifted to the FIG. 3 position to isolate the cylinders of the servomotor means.

In the illustrated embodiment of FIGS. 1 and 2, two sets of independently operable means (mounts 14a, 14b, arms 12a, 12b, springs 16a, 16b and servomotor-servovalve means) support the ends of the dancer roll 10. This arrangement aflords an extremely sensitive control for accurately positioning the dancer roll to compensate for variations in web tension. It is apparent, however, that if the mounting means 14 is formed as one unit and if the arm means 12 is interconnected for simultaneous pivotal movement, the previously described tension control operation could be achieved with the use of a single servovalve and servomotor.

The embodiment of FIGS. 1 and 2 is particularly suitable for use in tensioning low tension webs of a thin sheet material. The invention reduces the deleterious effects of the mass of the dancer roll and the associated support means on web tension control. In this regard, it should be noted that in the equilibrium position illustrated in FIG. 1, the arm means 12 are vertical and the weight of the dancer roll is centered over the pivot axis. Consequently, the weight of the dancer roll has no lateral component causing pivotal movement of the arms relative to the mounting means.

In the prior art apparatus, it is common practice to movably support the dancer roll either by pivot arms, as previously described, or by slidably mounted bearing blocks. An embodiment of the present invention including the latter characteristic is shown in FIG. 4 wherein the dancer roll 10 is journaled at each end in vertically movable bearing block means 12 to tension the continuous Web W. The means for supporting the ends of the dancer roll are identical, and consequently only one need be described. The bearing block means 12' is slidably mounted for vertical reciprocatory movement relative to mounting means 14', and is biased toward the desired position by spring means 16'. Stop means 20, on the mounting means 14, limits the movement of the bearing block means 12' under pressure of the spring means 16.

In accordance with the present invention, the mounting means 14 is slidably mounted for movement relative to vertically disposed bedrail means 18, and is positioned by motor means 24' controlled by means 22' carried by mounting means 14 and subject to actuation by bracket means 28 on the bearing block means 12'. Although this structure differs in appearance from that shown in FIG. 1, the parts are equivalent and function in like manner so that a detailed description is deemed unnecessary. However, equivalent parts are given like reference characters except that those in FIG. 4 are primed.

For purposes of illustration, the stop means 20 is shown as adjustable and is constituted by screw means, and the bracket means 28 is provided with adjustable abutment means 80, namely screw means, for engagement by the plunger means 26' of the valve means 22.

\Vith the vertically movable mounting means 14, the motor means 24' need not comprise a servomotor but can be constituted by fluid operated jack means which is fluid pressure operated only in the upward direction and gravity operated in the downward direction. In this event, the conduit 68 can be eliminated and the cylinder pening 40' vented to atmosphere.

In operation, when the various elements are in the positions illustrated in FIG. 4 with the valve means 22 in the position illustrated in FIG. 3, the spring means 16' counterbalances the downwardly directed force resulting from the weight of dancer roll and the initial web tension. Consequently, roll 10 and bearing block means 12 have a given initial equilibrium position relative to mounting means 14-. Should web tension increase, roll 10' is displaced downwardly against the force of spring means 16, and the valve plunger is displaced downwardly to effect momentary venting of the lower chamber of motor means 24, whereupon mounting means 14 is displaced downwardly to relieve web tension. Dancer roll 10 is displaced downwardly until the tension of spring means again balances web tension, and roll 1% is in the equilibrium position relative to mounting means 14, whereupon valve means 22' is closed automatically.

On the other hand, if web tension decreases, the dancer roll is moved upwardly by spring means 10, valve means 22' is operated to pressurize the lower chamber of motor means 24, and vent the upper chamber if necessary, and mounting means 14 is moved upwardly until the mounting means and dancer roll again have the same relative equilibrium position. Ifdesired, the system of FIG. 4 may be designed for operation by a singe motor and valve means as described with regard to the embodiment of FIGS. 1 and 2.

Although certain specific embodiments of the invention have been shown and described, it is obvious that many modifications thereof are possible. The invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

What is claimed is:

1. Web tensioning apparatus, comprising a dancer roll around which a continuous web is to be trained, support means journaling said dancer roll, mounting means movably supporting said support means to enable movement of said dancer roll in accordance with variations in web tension, spring means between said support means and said mounting means and continuously biasing said dancer roll in web-tensioning direction and establishing a given initial equilibrium position of said roll relative to said mounting means, bed means movably supporting said mounting means for reciprocatory movement generally parallel to the path oi roll movement, and means responsive to movement of said dancer roll from said initial relative equilibrium position for displacing said mounting means to return said dancer roll to said relative equilibrium position, whereby the web tension is maintained constant.

2. Web tensioning apparatus according to claim 1 wherein said responsive and displacing means comprises valve means disposed on said mounting means to sense movement of said dancer roll, and fluid operated motor means controlled by said valve means and connected with said mounting means.

3. Web tensioning apparatus according to claim 2 wherein said valve means comprises servovalve means having spring biased operating plunger means engaging said support means, and said fluid operated motor means comprises servomotor means.

4. Apparatus as defined in claim 3 wherein said support means comprises pivot arm means pivotally connecting said dancer roll with said mounting means, said servovalve means being mounted on said mounting means for operation by said pivot arm means.

5. Apparatus as defined in claim 4 wherein the path of reciprocation of said mounting means is horizontal and said pivot arm means extends upwardly and is disposed vertically when said roll is in the given initial equilibrium position.

6. Apparatus as defined in claim 2 wherein said support means comprises bearing block means slidably connected with said mounting means, said responsive means comprising valve means mounted on said mounting means for operation in response to movement of said bearing block means.

7. Apparatus as defined in claim 6 wherein said paths of reciprocation of said bearing block means and said mounting means are vertical, and said spring means is interposed therebetween to bias said bearing block means upwardly relative to said mounting means.

8. Web tensioning apparatus, comprising horizontally disposed stationary bedrail means, mounting means mounted for reciprocation on said bedrail means, a dancer roll around which a continuous web is trained, arm means pivotally mounted on said mounting means for supporting said dancer roll above said mounting means for pivotal movement in a plane normal to the axis of said roll and generally parallel with said bedrail means, spring means between said mounting means and said arm means and pivotally biasing said dancer roll in the web tensioning direction relative to said mounting means, whereby for a given initial position of said mounting means and for a given initial web tension, said dancer roll and said arm means have a given equilibrium position extending substantially vertically relative to said mounting means and in which the web tension is counterbalanced by said spring means, servovalve means on said mounting means and responsive to movement of said arm means from said equilibrium position, and servomotor means controlled by said servovalve means for displacing said mounting means relative to said bedrail means to return said arm means to said equilibrium position relative to said mounting means, whereby uniform web tension is maintained.

9. Web tensioning apparatus, comprising a stationary bed, mounting means connected for vertical reciprocatory movement relative to said bed, a dancer roll over which a continous web is to be trained and connected for vertical reciprocatory movement relative to said mounting means, said dancer roll being arranged for upward movement to apply tension to the web, spring means carried by said mounting means and biasing said dancer roll upwardly relative to said mounting means whereby for a given initial position of said mounting means and for a given initial web tension, said dancer roll has an equilibrium position relative to the mounting means in which the web tension is counter-balanced by said spring means, valve means responsible to displacement of said dancer roll from said equilibrium position, and fluid operated motor means controlled by said valve means for shifting said mounting means relative to said bed to return said dancer roll to said equilibrium position relative to said mounting means, whereby uniform web tension is maintained.

No references cited.

ROBERT B. REEVES, Primary Examiner. F. R. HANDREN, Assistant Examiner. 

1. WEB TENSIONING APPARATUS COMPRISING A DANCER ROLL AROUND WHICH A CONTINUOUS WEB IS TO BE TRAINED, SUPPORT MEANS JOURNALING SAID DANCER ROLL, MOUNTING MEANS MOVABLY SUPPORTING SAID SUPPORT MEANS TO ENABLE MOVEMENT OF SAID DANCER ROLL IN ACCORDANCE WITH VARIATIONS IN WEB TENSION, SPRING MEANS BETWEEN SAID SUPPORT MEANS AND SAID MOUNTING MEANS AND CONTINUOUSLY BIASING SAID DANCER ROLL IN WEB-TENSIONING DIRECTION AND ESTABLISHING A GIVEN INITIAL EQUILIBRIUM POSITION OF SAID ROLL RELATIVE TO SAID 